org.mmtk.plan.semispace

Class SS

java.lang.Object

org.mmtk.plan.Plan

org.mmtk.plan.Simple

org.mmtk.plan.StopTheWorld

org.mmtk.plan.semispace.SS

Direct Known Subclasses:

GCTrace, SSGCspy, UsePrimitiveWriteBarriers

public class SS
extends StopTheWorld

This class implements a simple semi-space collector. See the Jones & Lins GC book, section 2.2 for an overview of the basic algorithm. This implementation also includes a large object space (LOS), and an uncollected "immortal" space.

All plans make a clear distinction between global and thread-local activities. Global activities must be synchronized, whereas no synchronization is required for thread-local activities. Instances of Plan map 1:1 to "kernel threads" (aka CPUs). Thus instance methods allow fast, unsychronized access to Plan utilities such as allocation and collection. Each instance rests on static resources (such as memory and virtual memory resources) which are "global" and therefore "static" members of Plan. This mapping of threads to instances is crucial to understanding the correctness and performance properties of this plan.

Field Summary

Fields

Modifier and Type	Field and Description
static int	ALLOC_SS
static CopySpace	copySpace0 One of the two semi spaces that alternate roles at each collection
static CopySpace	copySpace1 One of the two semi spaces that alternate roles at each collection
static boolean	hi true if allocating into the "higher" semispace
static int	SCAN_SS
static int	SS0
static int	SS1
Trace	ssTrace

Fields inherited from class org.mmtk.plan.StopTheWorld

postSanityPhase, preSanityPhase

Fields inherited from class org.mmtk.plan.Simple

CLOSURE, collection, collectionAttempt, COMPLETE, completeClosurePhase, FINALIZABLE, finishPhase, FORWARD, FORWARD_FINALIZABLE, FORWARD_REFS, forwardPhase, INITIATE, initPhase, PHANTOM_REFS, POST_SANITY_PLACEHOLDER, PRE_SANITY_PLACEHOLDER, PREPARE, PREPARE_STACKS, prepareStacks, refTypeClosurePhase, RELEASE, rootClosurePhase, ROOTS, SANITY_BUILD_TABLE, SANITY_CHECK_TABLE, SANITY_COPY_ROOTS, SANITY_PREPARE, SANITY_RELEASE, SANITY_ROOTS, SANITY_SET_POSTGC, SANITY_SET_PREGC, sanityBuildPhase, sanityCheckPhase, SET_COLLECTION_KIND, SOFT_REFS, STACK_ROOTS, WEAK_REFS, WEAK_TRACK_REFS

Fields inherited from class org.mmtk.plan.Plan

ALLOC_CODE, ALLOC_COLD_CODE, ALLOC_DEFAULT, ALLOC_GCSPY, ALLOC_HOT_CODE, ALLOC_IMMORTAL, ALLOC_LARGE_CODE, ALLOC_LOS, ALLOC_NON_MOVING, ALLOC_NON_REFERENCE, ALLOC_PRIMITIVE_LOS, ALLOC_STACK, allocationSiteCount, ALLOCATORS, concurrentWorkers, controlCollectorContext, DEFAULT_MAX_NURSERY, DEFAULT_MIN_NURSERY, DEFAULT_SITE, defaultCollectorContext, emergencyCollection, GATHER_WRITE_BARRIER_STATS, GC_PREPARE, GC_PROPER, IMMORTAL, immortalSpace, insideHarness, internalTriggeredCollection, LARGE_CODE, largeCodeSpace, lastInternalTriggeredCollection, LOS, loSpace, MAX_NON_LOS_COPY_BYTES, MAX_NON_LOS_DEFAULT_ALLOC_BYTES, MAX_NON_LOS_NONMOVING_ALLOC_BYTES, META, metaDataSpace, NEEDS_LOG_BIT_IN_HEADER, NON_MOVING, NON_PARTICIPANT, nonMovingSpace, NOT_IN_GC, parallelWorkers, pretenureThreshold, SANITY, sanityChecker, sanitySpace, SCAN_BOOT_IMAGE, SMALL_CODE, smallCodeSpace, stacksPrepared, totalTime, USE_CODE_SPACE, userTriggeredCollection, VM_SPACE, vmSpace

Constructor Summary

Constructors

Constructor and Description
SS() Constructor

Method Summary

Modifier and Type	Method and Description
void	collectionPhase(short phaseId) Perform a (global) collection phase.
static CopySpace	fromSpace()
int	getCollectionReserve() Return the number of pages reserved for copying.
int	getPagesAvail() Return the number of pages available for allocation, assuming all future allocation is to the semi-space.
int	getPagesUsed() Return the number of pages reserved for use given the pending allocation.
protected void	registerSpecializedMethods() Registers specialized methods.
static CopySpace	toSpace()
boolean	willNeverMove(ObjectReference object) Can this object ever move.

Methods inherited from class org.mmtk.plan.StopTheWorld

processOptions

Methods inherited from class org.mmtk.plan.Simple

replacePhase, replacePlaceholderPhase, switchNurseryZeroingApproach

Methods inherited from class org.mmtk.plan.Plan

availableMemory, bootTimeWriteBarrier, collectionRequired, concurrentCollectionRequired, determineThreadCount, enableAllocation, enableCollection, forceFullHeapCollection, freeMemory, fullyBooted, gcInProgress, gcInProgressProper, getAllocationSite, getPagesReserved, getSpecializedScanClass, getTotalPages, handleUserCollectionRequest, harnessBegin, harnessEnd, insertPhaseAfter, isCurrentGCNursery, isEmergencyCollection, isInitialized, isInternalTriggeredCollection, isUserTriggeredCollection, lastCollectionFullHeap, lastCollectionWasExhaustive, loadObjectReference, logPoll, notifyExit, poll, preCollectorSpawn, printDetailedTiming, printPostStats, printPreStats, printUsedPages, reservedMemory, resetCollectionTrigger, sanityExpectedRC, sanityLinearScan, setBuildTimeGCByte, setGCStatus, spawnCollectorThreads, stacksPrepared, startGCspyServer, storeObjectReference, stressTestGCRequired, totalMemory, triggerInternalCollectionRequest, usedMemory

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

hi

public static boolean hi

true if allocating into the "higher" semispace

copySpace0

public static final CopySpace copySpace0

One of the two semi spaces that alternate roles at each collection

SS0

public static final int SS0

copySpace1

public static final CopySpace copySpace1

One of the two semi spaces that alternate roles at each collection

SS1

public static final int SS1

ssTrace

public final Trace ssTrace

ALLOC_SS

public static final int ALLOC_SS

See Also:

Constant Field Values

SCAN_SS

public static final int SCAN_SS

See Also:

Constant Field Values

Constructor Detail

SS

public SS()

Constructor

Method Detail

toSpace

public static CopySpace toSpace()

Returns:

The to space for the current collection.

fromSpace

public static CopySpace fromSpace()

Returns:

The from space for the current collection.

collectionPhase

public void collectionPhase(short phaseId)

Perform a (global) collection phase.

Overrides:

collectionPhase in class Simple

Parameters:

phaseId - The unique id of the phase to perform.

getCollectionReserve

public final int getCollectionReserve()

Return the number of pages reserved for copying.

Overrides:

getCollectionReserve in class Plan

Returns:

The number of pages reserved given the pending allocation, including space reserved for collection.

getPagesUsed

public int getPagesUsed()

Return the number of pages reserved for use given the pending allocation. This is exclusive of space reserved for copying.

Overrides:

getPagesUsed in class Plan

Returns:

The number of pages reserved given the pending allocation, excluding space reserved for copying.

getPagesAvail

public final int getPagesAvail()

Return the number of pages available for allocation, assuming all future allocation is to the semi-space.

Overrides:

getPagesAvail in class Plan

Returns:

The number of pages available for allocation, assuming all future allocation is to the semi-space.

willNeverMove

public boolean willNeverMove(ObjectReference object)

Description copied from class: Plan

Can this object ever move. Used by the VM to make decisions about whether it needs to copy IO buffers etc.

Overrides:

willNeverMove in class Plan

Parameters:

object - The object in question

Returns:

true if it is not possible that the object will ever move.

registerSpecializedMethods

protected void registerSpecializedMethods()

Description copied from class: Plan

Registers specialized methods.

Overrides:

registerSpecializedMethods in class Plan